21001100021001 has 24 divisors (see below), whose sum is σ = 31040869745600. Its totient is φ = 13674921585696.

The previous prime is 21001100020969. The next prime is 21001100021071. The reversal of 21001100021001 is 10012000110012.

It is a happy number.

It is not a de Polignac number, because 21001100021001 - 2⁵ = 21001100020969 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001100021071) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 26654100 + ... + 27430698.

Almost surely, 2^{21001100021001} is an apocalyptic number.

It is an amenable number.

21001100021001 is a deficient number, since it is larger than the sum of its proper divisors (10039769724599).

21001100021001 is a wasteful number, since it uses less digits than its factorization.

21001100021001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 846525 (or 846522 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21001100021001 its reverse (10012000110012), we get a palindrome (31013100131013).

The spelling of 21001100021001 in words is "twenty-one trillion, one billion, one hundred million, twenty-one thousand, one".